An RC-IGBT includes a gate terminal, a collector terminal (drain terminal), and an emitter terminal (source terminal). An RC-IGBT can be operated in a forward biased mode, which is when an internal pn-junction between a body region and a drift region of the RC-IGBT is reverse biased, and in a reverse biased mode, which is when the pn-junction is forward biased. In the forward biased mode, the RC-IGBT only conducts a current when a suitable drive potential is applied to the gate terminal, while in the reverse biased mode, the RC-IGBT conducts a current independent of the control of the gate terminal. In the reverse biased mode, the RC-IGBT operates like a diode that may cause reverse-recovery losses when the RC-IGBT is commutated from the reverse biased mode, which is when the body diode is conducting, to the forward-biased mode, which is when the body diode is reverse biased. Commutation in this context means that the voltage applied to the load terminals of the power device, e.g. the RC-IGBT, changes its sign (polarity) due to an external electrical circuit.
Reverse recovery losses may also occur in a bipolar diode when it is commutated from a forward biased state to a reverse biased state, and in a MOSFET when an integrated body diode is commutated from a forward biased state to a reverse biased state.
It is basically desirable to reduce those reverse recovery losses.